Pigment manufacture



Patented Sept. 1, 1942 PIGMENT MANUFACTURE Sylvester A. Scully, NewMilford, N. J., assignor to Interehemical Corporation, New York, N. Y.,a corporation of Ohio No Drawing. Substituted for abandoned applicationSerial No. 314,047, January 16, 1940. This application August 8, 1941,Serial No. 406,007

2 Claims.

This invention relates to the pigment prepared by coupling tetrazotizeddianisidine with Schaeffers salt (2 naphthol-6 sulfonic acid) andpreparing a metal complex therefrom, and has particular reference to amethod of preparing the pigment in high concentration aqueous slurry.

This pigment (and others of similar nature) is extremely hydrophile andorganophobe. When it is dried, it cannot be dispersed in hydrophobicorganic media; and it cannot be flushed from an aqueous pulp into ahydrophobe organic system. It has been proposed to disperse this pigmentin such a system by malaxating a filter press cake with an organiccolloid on an open mill such as a rubber compounding roll. The method issuccessful, but expensive, due to the fact that filter press cakes ofthis pigment generally contain about -10% of pigment, necessitating theevaporation of from 9' to 19 parts of water for each part of pigment.

I have discovered a method of producing this pigment in such form thatpress cakes of 20-30% pigment content can be readily prepared. Thismethod comprises coupling tetrazotized dianisidine with Schaefiers saltin an acid medium, followed by conversion of the pulp to the alkalinestate'to develop its color, following which the pigment is laked with acopper or other salt.

A typical example of the method is the following:

6.1 pounds of dianisidine are slurried in 18 gallons of water and 14.3pounds of 20 Baum hydrochloric acid is added. The mass is stirred untilhydrochloride formation is complete, and then the whole is iced to 05 C.A solution of 3.75 pounds of sodium nitrite dissolved in 4-5 gallons ofwater is then added slowly, thus tetrazotizing to a strong positivereaction to starch- KI paper. When tetrazotization is complete, 15pounds of sodium acetate dissolved in water is added and stirred inwell. The resulting solution should show no reaction to Congo red paper.This is then diluted to 60 gallons. This solution is added over a periodof 20-25 minutes to a solution of 12.3 pounds Schaeffers salt (betanaphthol-S-sulfonic acid) in a total of 90 gallons of water at 0-5 C.There is formed a dull maroon pigment of fairly large particle size.This suspension is stirred for at least one-half hour. There is thenadded 12.5 pounds of 28% ammonium hydroxide to distinct alkalinity,whereupon there is formed a blue pigment, the

particle size and. other characteristics of which,

even after treating with a copper sulfate solution (17.5 pounds as asolution) lend to easier and more rapid filtration and washing. Thepigment concentration in a filter press cake thus prepared approximates-'30%.

I believe that the increased solid content of the press cake is due tothe fact that the pigment is first separated as the maroon pigment,which is probably only partally coupled, and that the blue pigmentformed on the addition of the ammonium hydroxide takes the form Of theoriginal precipitate, instead of the form it would take if prepareddirectly, in conventional fashion.

The method may be varied considerably, the important point being tocause the original coupling to take place in a bufiered acid solution,at a pH above about 4.0 and below 7.0, and to pro- 4 duce the final bluepigment by a change in the already precipitated maroon color.

The blue finally produced may be coppered, or may be metallized withmany other metal salts, including those of the alkali metals, the alkaliearth metals, nickel, cobalt, zinc, copper, manganese, iron, aluminum,and chromium.

Various modifications can of course be made in my invention withoutdeparting from its scope, which is defined in the claims.

This application is a substitute for abandoned application Serial No.314,047, filed January 16, 1940.

I claim:

1. The method of producing a high solids aqueous pulp of the pigmentobtained by coupling tetrazo dianisidine with 2 naphthol 6 sulfonicacid, which comprises initially coupling the components in a bathmaintained at a pH of from about 4.0 to about 7.0, whereby a maroonpigment is formed, thereafter adding an alkali to the bath whereby thepigment is converted to a blue color, and thereafter metallizing thepigment.

2. The method of producing a high solids aqueous pulp of the pigmentobtained by coupling tetrazo dianisidine with 2 naphthol 6 sulfonicacid, which comprises initially coupling the compounds in a bathmaintained at a pH of from about 4.0 to about 7.0,whereby a maroonpigment is formed, thereafter adding an alkali to the bath whereby thepigment is converted to a blue color, and thereafter metallizing thepigment with a copper salt.

SYLVESTER A. SCULLY.

CERTIFICATE OF CORRECTION.

Patent No. 2,29L u26. September 1, 19L 2.

SYLVESTER A SCULLY lt is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows: Page 1, sec- 0nd column, line 9, for "partally" read-partia'l1y; line 14.7, for "compounds" read --components--; and thatthe said Letters Patent should be read with this correction therein thatthe same may conform to the record of the case in the Patent Office. 7

Signed and sealed this 15th day of October, A. D. 19L 2.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.

